In order to enhance the image taken by the camera in night environment, an adaptive night scene enhancement system combined with analog circuit is designed. Firstly, the analog camera captures the video. Next, the AD603 chip amplifies the captured analog video signal decoded by the TVP5150 chip that outputs the data in the ITU-R BT.656 format. Then, the FPGA performs effective data extraction, resolution modification and preprocessing such as video pin. Finally, the adaptive algorithm and D/A conversion circuit control the AD603 chip to adjust the magnification to achieve the system’s adaptive adjustment to the surrounding environment, so that the average gray value of each frame of image is stabilized near the set threshold. The paper uses hardware circuits instead of complex software algorithms to achieve results, while it greatly reduces FPGA resource consumption and implements the design on the ALINX AX545 FPGA platform. The experimental results show that at the resolution of 640×480 and 60 frame/s, it can perform adaptive real-time enhancement of night images, and finally stabilize the average gray value of the image near the set threshold. The system can be applied in the fields of target detection and video surveillance.